Radiation-induced polymerization and grafting of β(−)pinene on silica surface

Poly-β-pinene (pBp) was obtained on silica surface by γ radiation-induced polymerization of β(−)pinene in presence of silica gel with a specific surface area of 300 m²/g. Different radiation doses were employed in the range 50–332 kGy. The pBp–silica hybrid samples obtained have been characterized by FT-IR spectroscopy and the amount of pBp on silica surface has been determined both by gravimetric and TGA measurements. The fraction of pBp chemically grafted on silica surface has been determined by the extraction of the pBp–silica hybrid with boiling toluene and was found to be 10–20% of the total pBp formed on silica surface. The optical activity of pBp extracted from the hybrid was studied by polarimetric measurements and found slightly lower than the typical specific optical rotation of pBp polymerized in bulk with radiation. The thermal stability of the pBp–silica hybrid materials was studied by thermogravimetric and differential thermal analysis. The results show lower thermal stability for the pBp–silica hybrid in comparison to pure pBp. Evidently, silica catalyzes the thermal decomposition of pBp at lower temperatures. Use of the pBp–silica hybrid as stationary phase for liquid chromatography for chiral separations has been proposed.     

Efficient Adsorption of Chromium Ions from Aqueous Solutions by Plant-Derived Silica

Nowadays, there is great interest in the use of plant waste to obtain materials for environmental protection. In this study, silica powders were prepared with a simple and low-cost procedure from biomass materials such as horsetail and common reed, as well as wheat and rye straws. The starting biomass materials were leached in a boiling HCl solution. After washing and drying, the samples were incinerated at 700 °C for 1 h in air. The organic components of the samples were burned leaving final white powders. These powders were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM), and low-temperature nitrogen sorption. The amorphous powders (biosilica) contained mainly SiO₂, as indicated by FTIR analysis. Horsetail-derived silica was chosen for testing the removal of dichromate ions from water solutions. This biosilica had a good ability to adsorb Cr(VI) ions, which increased after modification of the powder with the dodecylamine surfactant. It can be concluded that the applied procedure allowed obtaining high purity biosilica from plant waste with good efficiency. The produced biosilica was helpful in removing chromium ions and showed low cytotoxicity to human endothelial cells, suggesting that it can be safely used in environmental remediation.     

Selective separation and determination of quercetin from red wine by molecularly imprinted nanoparticles coupled with HPLC and ultraviolet detection

In this study, a highly sensitive and selective sample pretreatment procedure using molecularly imprinted silica nanoparticles was developed for the extraction and determination of quercetin in red wine samples coupled with high‐performance liquid chromatography with ultraviolet detection. The imprinted silica nanoparticles were prepared in the presence of N‐acryoyl‐l ‐aspartic acid (functional monomer), quercetin (template), azobisisobutyronitrile (initiator) and methylene bisacrylamide (cross‐linker) and methanol/water (porogen) via surface‐initiated reversible addition‐fragmentation chain transfer polymerization. Surface characterization was performed and several imprinting parameters were investigated, and the results indicated that adsorption of quercetin on the imprinted silica nanoparticles followed a pseudo‐first‐order adsorption isotherm with a maximum adsorption capacity at 26.4 mg/g within 60 min. The imprinted silica nanoparticles also showed satisfactory selectivity towards quercetin as compared with its structural analogues. Moreover, the imprinted nanoparticles preserved their recognition ability even after five adsorption–desorption cycles. Meanwhile, the nanoparticles were successfully applied to selective extraction of quercetin from red wine with a high recovery (99.7–100.4%). The limit of detection was calculated to be 0.058 μg/mL with a correlation coefficient 0.9996 in the range of 0.2–50 μg/mL. As a result, the developed selective extraction method using molecular imprinting technology simplifies the sample pretreatment procedure before determination of quercetin in real samples.     

Influence of surfactant surface coverage and aging time on physical properties of silica nanoparticles

The experimental results on the influence of surfactant surface coverage and aging time on physical properties of silica nanoparticles were reported. The spherical silica nanoparticles have been synthesized using polyethylene glycol (PEG) as the surfactant and oil shale ash (OSA) as a new silica source. In order to identify the optimal condition for producing the best quality silica nanoparticles with the good dispersion and uniformity, the effects of surfactant surface coverage and aging time were investigated. It was found that the particle size and distribution of silica nanoparticles depend on the concentration of PEG in dispersion. At relatively low concentration, 0–2 wt.%, the existing PEG is not sufficient to prevent further growth of the initially formed silica nanoparticles, leading to large aggregates of silica particles. When the PEG concentration increases to 3 wt.%, self-assembled PEG layer on the surface stabilizes the initially formed silica nanoparticles and the silica particles with average diameter of 10 nm are uniformly distributed. With further increasing the concentration of PEG, the number of PEG aggregates increases and silica nanoparticles are mainly formed inside the entangled PEG chains, resulting in an observation of clusters of silica nanoparticles. Moreover, it was found that as the aging time increased, the shape of silica nanoparticles becomes regular and the particle size distribution becomes narrow.     

Identification of organically associated trace elements in wood and coal by inductively coupled plasma mass spectrometry

1-Methyl-2-pyrrolidinone (NMP) was used to extract samples of wood (forest residue) and coal; the extracts were analysed by inductively coupled plasma mass spectrometry (ICP-MS) using two different sample preparation methods, in order to identify trace elements associated with the organic part of the samples. A sample of fly ash was similarly extracted and analysed in order to assess the behaviour of the mineral matter contained within the wood and coal samples. 32% of the biomass was extracted at the higher temperature and 12% at room temperature while only 12% of the coal was extracted at the higher temperature and 3% at room temperature. Less than 2% of the ash dissolved at the higher temperature. Size exclusion chromatograms of the extracts indicated the presence of significant amounts of large molecular mass materials (>1000 mu) in the biomass and coal extracts but not in the ash extract. Trace element analyses were carried out using ICP-MS on the acid digests prepared by 'wet ashing' and microwave extraction. Sixteen elements (As, Ba, Be, Cd, Co, Cr, Cu, Ga, Mn, Mo, Ni, Pb, Sb, Se, V and Zn) were quantified, in the samples before extraction, in the extracts and in the residues. Concentrations of trace elements in the original biomass sample were lower than in the coal sample while the concentrations in the ash sample were the highest. The major trace elements in the NMP extracts were Ba, Cu, Mn and Zn from the forest residue; Ba, Cu, Mn, Pb and Zn from the coal; Cu and Zn from the ash. These elements are believed to be associated with the organic extracts from the forest residue and coal, and also from the ash. Be and Sb were not quantified in the extracts because they were present at too low concentrations; up to 40% of Mn was extracted from the biomass sample at 202 degrees C, while Se was totally extracted from the ash sample. For the forest residue, approximately 7% (at room temperature) and 45% (at 202 degrees C) of the total trace elements studied were in the extract; for the coal, approximately 8% (at room temperature) and 23% (at 202 degrees C) were in the extract. For the ash, only 1.4% of the trace elements were extracted at 202 degrees C, comprising 25% of Cd but less than 1% of Pb.     

A simple template-free sol–gel synthesis of spherical nanosilica from agricultural biomass

Mesoporous silica nanoparticles with a spherical morphology have been synthesized from rice husk (agricultural biomass) by a simple, template-free synthetic approach, which was carried out via sol–gel technique at ambient condition. Transmission electron micrographs revealed the formation of spherical silica nanoparticles with an average diameter of 50.9 nm. From the nitrogen adsorption–desorption analysis, the rice husk silica shows a high specific BET surface area of 245 m² g⁻¹. The silica nanoparticles have a narrow pore size distribution of 5.6–9.6 nm.     

Sulfonated silica‐based electrolyte nanocomposite membranes

New functionalized particles were prepared by attaching sulfonated aromatic bishydroxy compounds onto fumed silica surface. First, a bromophenyl group was introduced onto the silica surface by reaction of bromophenyltrimethoxysilane with fumed silica. Then, sulfonated bishydroxy aromatic compounds were chemically attached to the silica surface by nucleophilic substitution reactions. The structure of the modified silica was characterized by elemental analysis: ¹³C‐NMR, ²⁹Si‐NMR, and FTIR. Afterward, novel inorganic–organic electrolyte composite membranes based on sulfonated poly(ether ether ketone) have been developed using the sulfonated aromatic bishydroxy compounds chemically attached onto the fumed silica surface. The composite membrane prepared using silica with sulfonated hydroxytelechelic, containing 1,3,4‐oxadiazole units, has higher proton conductivity values in all range of temperatures (40–140 °C) than the membrane containing only the plain electrolyte polymer, while the methanol permeability determined by pervaporation experiment was unchanged. A proton conductivity up to 59 mS cm^?1 at 140 °C was obtained. The combination of these effects may lead to significant improvement in fuel cells (fed with hydrogen or methanol) at temperatures above 100 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2278–2298, 2006     

Utilization of silica–chitosan nanocomposite for removal of 152+154Eu radionuclide from aqueous solutions

Journal of Radioanalytical and Nuclear Chemistry - Nano-silica (Si-AL800) was extracted from the thermally treated rice husk ash by acid leaching route. Coating surface of the extracted silica with...     

Facile synthesis and characterization of Fe2O3 nanoparticles using L-lysine and L-serine for efficient photocatalytic degradation of methylene blue dye

In this work, Fe₂O₃ nanoparticles, abbreviated as OL and OS, were facilely synthesized by the combustion procedure using L-lysine and L-serine as organic fuels, respectively. Also, the OL and OS samples were identified using different instruments such as Raman spectrometer, FT-IR spectrophotometer, UV–Vis spectrophotometer, XRD, HR-TEM, BET surface area, and FE-SEM. The XRD confirmed that the mean grain size of OL and OS samples is 42.23 and 33.16 nm, respectively. The HR-TEM images confirmed that irregular, hexagonal, and spherical shapes, have an average diameter of 39.13 and 34.28 nm, were observed in the OL and OS samples, respectively. The BET surface area of the OL and OS samples is 16.20 and 28.34 m²/g, respectively. Additionally, the OL and OS samples were accomplished for the photocatalytic degradation of methylene blue dye in the absence and presence of hydrogen peroxide. The % degradation of 45 mL of 25 mg/L of methylene blue dye in the case of using OL and OS samples in the absence of hydrogen peroxide is 55.23 and 63.64 % after 120 min, respectively. Also, in the presence of hydrogen peroxide, the % degradation in the case of using OL and OS samples is 100 % after 35 and 25 min, respectively.     

Molecularly imprinted magnetic nanoparticles for the micro solid‐phase extraction of thiabendazole from citrus samples

The preparation of molecularly imprinted core–shell magnetic nanoparticles and their subsequent use in the solid‐phase extraction of thiabendazole from citrus sample extracts is described. Molecularly imprinted core–shell magnetic nanoparticles were prepared by the precipitation copolymerization of the imprinting polymerization mixture on the surface of vinyl‐modified silica magnetic nanoparticles and were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The obtained molecularly imprinted core–shell magnetic nanoparticles exhibited a high selectivity for thiabendazole and were easily collected and separated by an external magnetic field without additional centrifugation or filtration steps. Under optimum conditions, a magnetic molecularly imprinted solid‐phase extraction method was developed allowing the extraction of thiabendazole from citrus sample extracts and final determination by high‐performance liquid chromatography with fluorescence detection. The detection limit was 0.2 mg/kg, far lower than the maximum residue limit established within the European Union for thiabendazole in citrus samples.     

Aerosol-assisted synthesis of mesoporous titania nanoparticles with high surface area and controllable phase composition

Mesoporous titania nanoparticles (denoted as MTN) with high surface area (e.g., 252 m² g⁻¹) were prepared using tetrapropyl orthotitanate (TPOT) as a titania precursor and 10–20 nm or 20–30 nm silica colloids as templates. Co-assembly of TPOT and silica colloids in an aerosol-assisted process and immediate calcination at 450 °C resulted in anatase/silica composite nanoparticles. Subsequent removal of the silica colloids from the composite by NaOH solution created mesopores in the TiO₂ nanoparticles with pore size corresponding to that of silica colloids. Effects of silica colloids’ contents on MTN porosity and crystallites’ growth at a higher calcination temperature (e.g., 1000 °C) were investigated. Silica colloids suppressed the growth of TiO₂ crystallites during calcination at a higher calcination temperature and controllable contents of the silica colloids in precursor solution resulted in various atomic ratios of anatase to rutile in the calcinated materials. The mesostructure and crystalline structure of these titania materials were characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD), differential thermal analysis (DTA)-thermo-gravimetric analysis (TGA), and N₂ sorption.     

C/粉煤灰复合吸附材料的制备及表征

以粉煤灰和蔗糖为原料,浓硫酸为炭化剂,制备了一种新型的C/粉煤灰复合吸附材料。 采用X光电子能谱、红外吸收光谱、场发射扫描电子显微镜、X射线衍射及N2气吸附实验对所制备复合材料进行了表征。 结果表明,粉煤灰表面被类石墨态炭纳米颗粒所包裹,复合材料表面密集分布着大量的介孔,Brunauer-Emmett-Teller(BET)比表面积SBET=5.4 m2/g,并且在该复合材料表面含有丰富的-SO3H、-COOH和-OH等含氧官能团。 考察了所制备的复合材料对典型阳离子型染料亚甲基蓝及重金属离子的吸附能力,结果表明,该复合材料具有优异的吸附性能,其对亚甲基蓝的吸附能力达到活性炭的83.7%,对典型重金属离子的吸附能力优于市售活性炭。 所制备复合材料可作为活性炭的一种替代品,用于水中有机染料和重金属离子的吸附处理。     

Non-linear modelling of the adsorption of Indigo Carmine dye from wastewater onto characterized activated carbon/volcanic ash composite

Over the past couple of years, the resurgence of placing an effective and sustainable amendment to combat against the auxiliary industrial entities like Indigo Carmine (IC), remains a highly contested agenda from a global point. The birth of non-linear modelling for these auxiliary entities is also of significant interest in order to avoid loss of some useful information. With the renaissance of activated carbon (AC), the AC prepared from palm kernel shells (PKSAC) and composite prepared by combining the PKSAC and porous volcanic ash (BVA) from the foot of active volcanic mountain of Cameroon will be of significant contribution for ever increasing pollution problems. Non-linear modelling method was used to model the uptake capacity by adsorption process of IC onto PKSAC and PKSAC/BVA composite. Effects of contact time (0–60 min), adsorbent dose, pH of solution and initial dye concentration (10–20 ppm) were studied on the quantity removal of the hazardous IC dye from aqueous solution in a batch experiment. The prepared PKSAC and PKSAC/BVA composite were characterized using Nitrogen adsorption at 77 K (BET), Fourier transform Infrared spectroscopy (FTIR), Sacanning electron microscopy with energy dispersive X Ray (SEM-EDX), and particle size. The optimum IC uptake was 11.025 and 12.642 mg/g for PKSAC and PKSAC/BVA composites adsorbent respectively. Four Isotherms and kinetic non-linear regression models each were used to model the adsorption data. It results that for the isotherm models, the Langmuir and Freundlich isotherm models best fitted the adsorption phenomenon while pseudo-first and pseudo-second order kinetic models well described the adsorption mechanism. Furthermore, the adsorption speed constant (α) of the Elovich kinetic model being higher than the desorption coefficient (β) implies chemisorption was the dominant mechanism in the adsorption process. The composite shows 14.67% higher in retention capacity of the IC dye than the pristine carbon. Conclusively, the expanding of activated carbon/volcanic ash composite represents a potentially viable and powerful tool, leading to the plausible improvement of environmental preservation.     

Isothermal and solution calorimetry to assess the effect of superplasticizers and mineral admixtures on cement hydration

The heat of hydration evolution of eight paste mixtures of various water to binder ratio and containing various pozzolanic (silica fume, fly ash) and latent hydraulic (granulated blast furnace slag) admixtures have been studied by means of isothermal calorimetry during the first 7 days of the hydration process and by means of solution calorimetry for up to 120 days. The results of early heat of hydration values obtained by both methods are comparable in case of the samples without mineral admixtures; the values obtained for samples containing fly ash and granulated blast furnace slag differ though. The results from isothermal calorimetry show an acceleration of the hydration process by the presence of the fine particles of silica fume and retarding action of other mineral admixtures and superplasticizer. The influence of the presence of mineral admixtures on higher heat development (expressed as joules per gram of cement in mixture) becomes apparent after 20 h in case of fly ash without superplasticizer and after 48 h for sample containing fly ash and superplasticizer. In case of samples containing slag and superplasticizer the delay observed was 40 h. The results obtained by solution calorimetry provide a good complement to the ones of isothermal calorimetry, as the solution calorimetry enables to study the contribution of the mineral admixtures to the hydration heat development at later ages of the hydration process, which is otherwise hard to obtain by different methods.     

Investigation of the effect of dual-size coatings on the hydrophobicity of cotton surface

A series of silica nanoparticles with two different length scales were introduced onto the cotton substrates to study the correlation between the surface structure and observed hydrophobicity. SiO₂ nanoparticles of 7, 12, 20, and 40 nm in size were individually functionalized using 3-aminopropyl triethoxysilane or 3-glycidoxypropyltrimethoxysilane. Amino functionalized silica nanoparticles were durably attached to the cotton surface that was previously treated with epichlorohydrin. By depositing an additional layer of epoxy modified silica nanoparticles, a dual-size hierarchical coating was obtained. It was found that the order of deposition of particles to develop dual-size coatings determines the surface roughness, hydrophobicity and the amount of silica loaded on the cotton substrate. Deposition of the bigger nanoparticles on top of smaller ones resulted in rougher surfaces, higher hydrophobicity and higher amount of silica loading onto the cotton surface. A strong correlation between the size ratio of deposited nanoparticle combinations and the amount of silica loading was observed. It was found that there is also a direct relationship between the surface roughness and the hydrophobicity of the samples generated. Based upon these correlations, it is now possible to tune surface roughness and subsequent wettability by controlling the sizes of the dual-type nanoparticle layers.     

Influence of thermal and UV treatment on the polypropylene/graphite composite

Electrically conductive polypropylene/graphite (PP/graphite) composites were prepared via blending granulated PP with maleic anhydride grafted PP and natural graphite. Electrical conductivity of prepared samples containing either 65, 70, or 75 wt% of graphite was measured and the most conductive sample containing 75 wt% of graphite was exposed to UV irradiation for 1 and 24 h or thermally treated at 170 °C for 1 h. The influence of thermal and UV exposure on the structural and electrical changes in such treated samples was studied. Local current measurements on the surface were made using scanning spreading resistance microscopy and morphology of the surface was studied by atomic force microscopy. X-ray diffraction analysis, infrared and Raman spectroscopy were also used for the structural characterization. Properties of treated and untreated samples are compared and differences are discussed.     

The effects of cerium doping concentration on the properties and photocatalytic activity of bimetallic Mo/Ce catalyst

In this study, the characterization and photocatalytic activity of MoO₃ nanoparticles doped with various doping concentrations of cerium have been investigated. The Fourier transform infrared (FT-IR) spectra of the prepared catalysts confirmed that MoO₃ particles have been successfully doped by cerium. Field emission scanning electron microscopy (FESEM) was performed to visualize the surface morphology of the obtained catalysts. The XRD patterns suggested that the crystallinity of the sample with the lowest doping concentration of 15 mol % was higher in comparison with samples of higher doping concentrations. The volume-averaged crystal sizes of the obtained catalysts were calculated to be 25, 28, and 32 nm for 15, 35, and 60 mol % samples, respectively. The photocatalytic activity along with the reaction kinetics of Ce-doped MoO₃ nanoparticles have also been investigated through the dye degradation of methyl orange. The synthesized Ce-doped MoO₃ particles with the lowest dopant concentration of 15 mol % exhibited the highest photocatalytic activity for methyl orange dye degradation. It was observed that photo-degradation activity decreased with an increase in the doping concentration of cerium. The predicted rate constants for samples with 15, 35, and 60 mol % doping concentrations were found to be 0.0432, 0.035, and 0.029 min^–1, respectively.     

Fungus-mediated biotransformation of amorphous silica in rice husk to nanocrystalline silica

Rice husk is a cheap agro-based waste material, which harbors a substantial amount of silica in the form of amorphous hydrated silica grains. However, there have been no attempts at harnessing the enormous amount of amorphous silica present in rice husk and its room-temperature biotransformation into crystalline silica nanoparticles. In this study, we address this issue and describe how naturally deposited amorphous biosilica in rice husk can be bioleached and simultaneously biotransformed into high value crystalline silica nanoparticles. We show here that the fungus Fusarium oxysporum rapidly biotransforms the naturally occurring amorphous plant biosilica into crystalline silica and leach out silica extracellularly at room temperature in the form of 2-6 nm quasi-spherical, highly crystalline silica nanoparticles capped by stabilizing proteins; that the nanoparticles are released into solution is an advantage of this process with significant application and commercial potential. Calcination of the silica nanoparticles leads to loss of occluded protein and to an apparently porous structure often of cubic morphology. The room-temperature synthesis of oxide nanomaterials using microorganisms starting from potential cheap agro-industrial waste materials is an exciting possibility and could lead to an energy-conserving and economically viable green approach toward the large-scale synthesis of oxide nanomaterials.     

Effects of surfactant/water ratio and dye amount on the fluorescent silica nanoparticles

Effects of surfactant/water volume ratios and dye amounts on the properties of micelles and fluorescence silica nanoparticles were studied in microemulsions containing nonionic surfactant Triton X-100, hexanol as co-surfactant, cyclohexane as organic solvent, and metal organic dye (tris(2,2′-bipyridyl)dichlororuthenium) via fluorescence probe technique, TEM, and XPS. Fluorescence probe measurements show that the micelle microenvironment becomes stable at the surfactant/water volume ratio higher than 3.5 and the incubation time longer than 10 h. The data suggest that the silica shell, which is formed at the surfactant/water ratio of 3.5, yields an efficient protection of dye molecules against the e-beam irradiation and result in high photostability of fluorescent silica. We pioneered the localization of dye molecules on the surface of dye-doped silica and found that an increase of dye amounts, beyond a threshold, in the microemulsion cannot enhance the fluorescence intensity of dye-doped nanoparticles. These results are of significant importance for optimizing the synthesis of fluorescent nanoparticles with high photostability and low cost.     

Modified generalized kinetic model and degradation mechanistic pathways for catalytic oxidation of NBS dye in Fenton-like oxidation process

Rice husk was utilized as a silica source for the synthesis of mesoporous silica (MS), which was further used for the surface modification of iron oxide nanoparticles (IO-NPs) to form mesoporous silica-modified iron oxide nanoparticles (MSIO-NPs). IO-NPs and MSIO-NPs were characterized using FT-IR, XRD, X-ray photoelectron spectroscopy, vibrating sample magnetometry, nitrogen adsorption–desorption, TEM and dynamic light scattering analysis. The catalytic activity of MSIO-NPs was tested for degradation and mineralization of Nile blue sulphate dye (NBS) in Fenton-like oxidation process. The degradation efficiency and total organic carbon (TOC) removal of NBS dye onto MSIO-NPs was found to be 92.46 and 66.58%, respectively, after 20 min of reaction time using 5 mM of H₂O₂ concentration. Modified generalized kinetic model was developed for TOC removal of dye degradation onto MSIO-NPs, to account for oxidizable compounds, non-oxidizable compounds, and intermediate organic compounds. The intermediate products formed during degradation of NBS dye were detected by LC–MS experiment and ten fragments were identified based on mass to charge ratio (m/z). The mechanistic pathway for degradation of NBS dye onto MSIO-NPs has been proposed.